Inhibition Of Radicle Growth Research Articles

The volatile-producing Flavobacterium johnsoniae strain GSE09 shows biocontrol activity against Phytophthora capsici in pepper

Previously, we selected a bacterial strain (GSE09) antagonistic to Phytophthora capsici on pepper, which produced a volatile compound (2,4-di-tert-butylphenol), inhibiting the pathogen. In this study, we identified strain GSE09 and characterized some of the biological traits of this strain in relation to its antagonistic properties against P. capsici. In addition, we examined bacterial colonization on the root surface or in rhizosphere soil and the effect of various concentrations of the volatile compound and strain GSE09 on pathogen development and radicle infection as well as radicle growth. Strain GSE09 was identified as Flavobacterium johnsoniae, which forms biofilms and produces indolic compounds and biosurfactant but not hydrogen cyanide (HCN) with little or low levels of antifungal activity and swimming and swarming activities. Fl. johnsoniae GSE09 effectively colonized on pepper root, rhizosphere, and bulk (pot) soil, which reduced the pathogen colonization in the roots and disease severity in the plants. Various concentrations of 2,4-di-tert-butylphenol or strain GSE09 inhibited pathogen development (mycelial growth, sporulation, and zoospore germination) in I-plate (a plastic plate containing a center partition). In addition, germinated seeds treated with the compound (1-100 μg ml⁻¹) or the strain (10²-10¹⁰ cells ml⁻¹) significantly reduced radicle infection by P. capsici without radicle growth inhibition. These results indicate that colonization of pepper root and rhizosphere by the Fl. johnsoniae strain GSE09, which can form biofilms and produce indolic compounds, biosurfactant, and 2,4-di-tert-butylphenol, might provide effective biocontrol activity against P. capsici. To our knowledge, this is the first study demonstrating that the Fl. johnsoniae strain GSE09, as a potential biocontrol agent, can effectively protect pepper plants against P. capsici infection by colonizing the roots.

Inhibition of Bacterial, Fungal, and Plant Growth by Testae Extracts of Citrullus Genotypes

Watermelon [Citrullus lanatus var. lanatus (Thunb.) Matsum & Nakai] seed and root exudates inhibit germination and seedling growth of plants and growth of pathogenic fungi and bacteria. This study was conducted to determine if extractable components in the testa (seedcoat) contribute to the inhibition previously reported. Testae of eight genetically diverse Citrullus genotypes were extracted first with dichloromethane to remove less polar components and then with 70% methanol to remove more polar components. The dichloromethane extracts were not inhibitory in a Proso millet radicle growth bioassay; however, they were highly inhibitory to the growth of the fruit blotch bacterial pathogen Acidovorax avenae subsp. citrulli (Aac). All dichloromethane extracts were highly inhibitory to Aac except those from a watermelon breeding line, 406-1-x 7 and a C. lanatus var. citroides accession, PI 500354. The more polar components extracted in 70% methanol inhibited Proso millet radicle and Aac growth and Phytophthora capsici zoospore germination. The greatest inhibition of radicle growth was found with 70% methanol extracts from two watermelon relatives, C. lanatus var. citroides [Bailey (Mansf.)] (PI 532738) and C. colocynthis [(L.) Scrad.] (PI 432337). They reduced radicle elongation by 90% at an extract concentration of 250 mg of tissue extracted per mL water. The 70% methanol extracts of several genotypes partially inhibited Aac colony formation, but the C. lanatus var. citroides accession, PI 532738, was the only genotype with 70% methanol extracts that completely inhibited the bacterium at 100 mg·mL−1. The 70% methanol extracts of Charleston Gray, 406-1-x 7, PI 500354, PI 532738, and PI 167125 were highly inhibitory in a Phytophthora capsici zoospore germination bioassay. These results indicate that the testae of Citrullus genotypes contain at least two compounds that are inhibitory to microorganisms and plants in bioassay, and the amount of inhibition caused by the extracts varied among Citrullus genotypes.

Physiological and antioxidant responses of germinating Cicer arietinum seeds to salt stress

Cicer arietinum (gram) is an important protein-rich pulse crop in Indian subcontinent, the Mediterranean region, Ethiopia, and Mexico. We studied the effects of different salt concentrations on radicle growth and different markers of oxidative stress, e.g., superoxide radical, MDA, protein carbonyls, as well as antioxidant compounds. Physiological and biochemical parameters were assessed in the radicles of germinating gram seeds after 1 and 7 days of treatments with 15, 30, 45, and 60 mM NaCl. The results showed that salt exerted a stronger effect (17-fold) on radicle length than on their dry weight (5-fold). This growth decrease was accompanied by an excessive (3-fold) accumulation of ROS and resulting protein carbonyl and MDA formation (3–6-fold). As to the responses of antioxidant compounds to salinity of the growing medium, all the enzymatic molecules (SOD, CAT, POX, and APX) showed significant (4–6-fold) reductions in their activities. Our results suggest that under salinity substantially higher amounts of oxidative stress markers (superoxide, MDA, and protein carbonyls) in collaboration with suppression of the ROS detoxification system ultimately led to gram radicle growth inhibition and severe oxidative stress.

Chemical characterization and phytotoxicity of volatile essential oil from leaves of Anisomeles indica (Lamiaceae)

Abstract The present study investigated the phytotoxic effect of foliar volatiles of Anisomeles indica . Laboratory bioassay with the detached leaves of A. indica inhibited the radicle and seedling elongation and dry weight accumulation of four test weeds, viz., Bidens pilosa, Cassia occidentalis, Amaranthus viridis and Echinochloa crus-galli depicting a dose–response relationship. On further investigation, yellowish-brown pungent smelling oil was extracted from the leaves. GC–MS analyses of the oil revealed 26 constituents with equal proportions of mono- and sesquiterpenes. α -Bisabolol oxide B, a sesquiterpene oxide, was the major component (∼21%) followed by dihydro- β -ionone, hexyl butanoate, tetracosane, and vitispirane (all > 5%). The oil inhibited radicle growth, seedling elongation and dry matter of the test weeds in a dose–response manner. The study concludes that foliar volatiles of A. indica emitted in the air suppress other plants, and may have several ecological implications like plant–plant interactions and the possibility of utilization for weed control.

Cytotoxic and growth inhibitory effects of the methanol extract Struchium sparganophora Ktze (Asteraceae) leaves.

Background:Global research into medicinal plants used in treating tumor-related ailments has become imperative due to the emergence of various forms of cancer diseases. Usually consumed as a vegetable, Struchium sparganophora is indicated in traditional herbal medicine as one of the plants used in treating tumor-related ailments.Materials and Methods:This claim was examined using bench-top assay methods involving the cytotoxicity of the methanol extract of the leaves to tadpoles of Raniceps ranninus at 10, 20, 40 and 80 μg/ml. Also, the growth inhibitory effects of the extract on guinea corn radicle at 0.5, 1.0, 2 and 4 mg/ml in addition to evaluation of the phytochemical constituents of the leaves was performed. After 24 h, the crude extract and the chloroform fraction produced the highest cytotoxicity of 96.67 ± 4.71%, each at a concentration of 80 μg/ml, while the aqueous fraction produced 100% cytotoxicity at a concentration of 20 μg/ml.Results:The crude extract had an LC50 of 26 μg/ml, the chloroform fraction had 6.25 while the aqueous fraction had 5 μg/ml. On the inhibition of the guinea corn radicle growth, after 96 h, the controls had an average length of 67.81 ± 2.6 mm, whereas the seeds treated with 4 mg/ml of the crude extract had an average length of 35.83 ±1.75 mm, indicating 47.81% reduction in length. At the same concentration, the chloroform and the aqueous fractions showed 32.51 and 43.81% inhibitions. The plant material was observed to contain alkaloids, tannins, saponins and flavonoids, with no traces of anthracene derivatives.Conclusion:The results suggest the probable use of the plant in preparing recipes for tumor-related ailments.

Effects of aqueous root extracts and hydrophobic root exudates of cucumber (Cucumis sativus L.) on nuclei DNA content and expression of cell cycle-related genes in cucumber radicles

Allelopathic interactions implicate the inhibition of cell division by allelochemicals. To examine the effects of autotoxic agents on cell cycle and plant growth, germinated cucumber seeds (Cucumis sativus L.) were incubated in solutions containing the aqueous root extracts of cucumber at 1:100, 1:50, 1:25 and 1:10 (w:v), or the hydrophobic root exudates of cucumber at 25, 50 and 100 mg·L−1. Aqueous root extracts and hydrophobic root exudates inhibited radicle elongation by 36.47–60.18% and 38.24–62.50%, respectively. The mitosis-specific genes were down-regulated in roots exposed to aqueous root extracts and hydrophobic root exudates. Meanwhile, exposure to either aqueous root extracts or hydrophobic root exudates decreased the proportion of 2C (C-value) and increased the proportion of 8C, leading to an increased mean C-value. We conclude that autotoxic agent-induced inhibition of radicle growth was partly attributed to the down-regulation of cell cycle-related genes and endoreduplication was enhanced under our experimental condition.

Phytotoxic effects of Sicyos deppei (Cucurbitaceae) in germinating tomato seeds

The phytotoxic effect of allelochemicals is referred to as allelochemical stress and it is considered a biotic stress. Sicyos deppei G. Don (Cucurbitaceae) is an allelopathic weed that causes phytotoxicity in Lycopersicon esculentum, delaying seed germination and severely inhibiting radicle growth. This paper reports in in vitro conditions, the effects of the aqueous leachate of S. deppei-throughout tomato germination times-on (1) the dynamics of starch and sugars metabolism, (2) activity and expression of the cell wall enzymes involved in endosperm weakening that allows the protrusion of the radicle, and (3) whether abscisic acid (ABA) is involved in this altered metabolic processes. Results showed that S. deppei leachate on tomato seed germination mainly caused: (1) delay in starch degradation as well as in sucrose hydrolysis; (2) lower activity of sucrose phosphate synthase, cell wall invertase, and alpha-amylase; being sucrose phosphate synthase (SPS) gene expression down-regulated, and the last two up regulated; (3) also, lower activity of endo beta-mannanase, beta-1,3 glucanase, alpha-galactosidase, and exo-polygalacturonase with altered gene expression; and (4) higher content of ABA during all times of germination. The phytotoxic effect of S. deppei aqueous leachate is because of the sum of many metabolic processes affected during tomato seed germination that finally is evidenced by a strong inhibition of radicle growth.

Suppression of Powell Amaranth (Amaranthus powellii) by Buckwheat Residues: Role of Allelopathy

Previous studies have demonstrated that emergence and growth of Powell amaranth is inhibited in soils where buckwheat has been grown and incorporated. The primary objectives of this research were to (1) evaluate the possible role of allelopathy in explaining that suppression; (2) distinguish between suppression caused by incorporation of fresh buckwheat residues from suppression caused by changes in soil during buckwheat growth; and (3) quantify the relative importance of buckwheat root vs. shoot tissues in suppression. When all buckwheat plant parts were removed from soil in which buckwheat was grown, Powell amaranth emergence was not suppressed, but growth was reduced 70% compared to bare soil. Addition of buckwheat shoots, but not roots to these soils reduced emergence by 80%, and contributed to additional reduction in growth. Addition of chemically activated carbon did not increase emergence or growth in buckwheat-amended soil. However, thermally activated carbon resulted in greater adsorption of phenolics than chemically activated carbon and alleviated suppression of Powell amaranth in buckwheat-amended, high organic-matter soils. However, suppression was not overcome on mineral soils. In addition to adsorbing phenolics, activated carbon changed the nitrogen (N) content and electrical conductivity of soil extracts. Aqueous shoot extracts of buckwheat stimulated Powell amaranth germination slightly, but inhibited radicle growth. Aqueous soil extracts from buckwheat-amended soil inhibited germination of Powell amaranth compared with extracts from unamended soil. Results suggest that emergence suppression of Powell amaranth by buckwheat residues might be due to allelopathic compounds concentrated in the shoot tissues. However, these inhibitory effects appear to depend on interactions of buckwheat residues with soils. In contrast, suppression of growth of Powell amaranth appears to be associated primarily with lower N availability in buckwheat-grown soils.

Antifeedant and Phytotoxic Activity of Hydroxyperezone and RelatedMolecules

The insect antifeedant and toxic activity of hydroxyperezone (1), its derivatives 2-9, along with 3-hydroxy- (10) and 6-hydroxythymoquinone (11) were studied against Spodoptera littoralis, Leptinotarsa decemlineata, and Myzus persicae. The antifeedant tests showed that L. decemlineata was the most sensitive insect, followed by M. persicae, while S. littoralis was not deterred by compounds 1-11. Leucohydroxyperezone tetraacetate (3), oxoperezinone (6), dihydroleucoperezinone diacetate (7), 3-hydroxy- (10) and 6-hydroxythymoquinone (11) showed strong activity against L. decemlineata. 1 and 7 exhibited moderate deterrent activity against M. persicae, while 1 and dihydroleucohydroxyperezone tetraacetate (4) acted as post-ingestive antifeedants to S. littoralis. The phytotoxic activity of compounds 1-11 was also evaluated. Hydroxyperezone (1) strongly inhibited seed germination at 24 h, while the activity of 3-8 and 10 was moderate. The level of radicle growth inhibition obtained with compounds 1-5 and 8-11 was significant (< 50%).

Phytotoxic activity and conformational analysis of thymol analogs from Hofmeisteria schaffneri

Bioassay-guided fractionation of two phytotoxic extracts (a CH 2Cl 2–MeOH (1:1) and an aqueous) prepared from the aerial parts of Hofmeisteria schaffneri led to isolation of thymol analogs 3– 5, along with seven known compounds, 1, 2 and 6– 10. Compounds 3– 5 were identified by spectroscopic methods as 1,4-bis(2′-hydroxy-4′-methylphenyl)butane-1,4-dione ( 3), 2-isopropyl-5-methylphenyl (2 Z)-2-methylbut-2-enoate ( 4) and 2-hydroxy-2-(2-hydroxy-4-methylphenyl)propane-1,3-diyl (2 Z,2′ Z)bis(2-methylbut-2-enoate) ( 5) and designated trivial names of hofmeisterins II–IV, respectively. Their conformational behavior was also studied by molecular modeling using density functional theory calculations at the B3LYP/DGDZVP level. Compounds 1– 4 and 6– 10 significantly inhibited radicle growth of seedlings of Amaranthus hypochondriacus and Echinochloa crus-galli in the Petri dish bioassay with IC 50’s ⩽ 10 −4 M. Furthermore, the northymol analog 3 provoked significant bleaching of seedlings of A. hypochondriacus. However, none of the isolates affected either seedling growth or germination of Medicago sativa.

Effects of Acetylsalicylic Acid on Germination, Growth and Chlorophyll Amounts of Cucumber (Cucumis sativus L.) Seeds

Germination activities, various growth parameters (primary root length, hypocotyl length, primary leaf length, plant length and increase in fresh weight) and chlorophyll (a+b) amounts of cucumber seeds exposed to 0, 10(-5), 10(-4), 10(-3) and 0.5x 10(-2) M aqueous solutions of acetylsalicylic acid (ASA) for 48 h were established. While 0.5x 10(-2) M ASA significantly prevented germination activity of the seeds, other concentrations did not produce any effect, either positive or negative. Meanwhile, 0.5x 10(-2) M ASA inhibited radicle growth of the germinated seeds, while 10(-5) M ASA increased radicle growth. Other concentrations of ASA did not affect radicle growth. The following findings were obtained from the one-week seedlings exposed to ASA for 48 h: 0.5x10(-2) M ASA prevented growth (lengthening) of root, hypocotyl, leaf and plant and increased chlorophyll (a+b) amount with an increase in fresh weight. Contrary to 0.5x 10(-2) M ASA application, these features of the seedlings (except for the leaf length) were encouraged by 10(-5) M ASA. 10(-3)) M ASA only prevented root growth and reduced chlorophyll (a+b) amount. Other concentrations of ASA did not bring about any positive or negative effect on the features studied.

Quantitative Cationic Activity Relationships for Predicting Toxicity of Metal Ions from Physicochemical Properties and Natural Occurrence Levels

AbstractQuantitative Cationic Activity Relationships (QCARs) were developed to predict the toxicity of metal ions from physicochemical properties and natural occurrence levels. In vivo toxicity data for different concentrations of nitrate salts of 17 metal ions were developed based on germination of sunflower seeds (F.1. Helianthus annuus ‘Sunspot’) in distilled water. The EC50 data were reported as the concentration giving 50% inhibition of radicle growth 1 day after emergence. Stepwise regression of the toxicity data produced correlations with some physicochemical properties and natural occurrence levels. For physicochemical properties, good results were obtained with the density of the elements, enthalpy of formation of metal sulphides and the stability constants of metal ions with sulphate ($\rm{ r_{{\rm{adj}}.}^2 }$=0.72−0.81). For natural occurrence levels, good results were obtained with metal concentrations in soil, the median elemental composition of soils and the calculated mean of the elemental content in land plants ($\rm{ r_{{\rm{adj}}.}^2 }$=0.69−0.83).

Regulation effect of Phyllostachys pubescens methanol extractives on growth of seed plants

Methanol extractives from moso bamboo (Phyllostachys pubescens) culms were found to have some regulation effects on the growth of the seed plants tested. They showed inhibition or promotion of hypocotyl and radicle growth of lettuce, watercress, and chrysanthemum. The methanol extractives were fractionated with n-hexane, diethyl ether, and ethyl acetate. The diethyl ether-soluble fraction contained more phenolic substances than the other fractions and showed strong inhibition of growth in lettuce seeds. The water-soluble fraction showed a promotion effect on the hypocotyl growth of lettuce. The water-soluble fraction was heated at 200°C for 8h, and the inhibition effect on the radicle growth of lettuce decreased and the promotion effect on the hypocotyl growth increased at 0.1% concentration.

Biological and biochemical detection techniques for glufosinate

Abstract Biological and biochemical methods, based on glufosinate inhibitory effects on plant growth and nitrogen metabolism, were examined for their applications to detect this herbicide. Dose–response analysis of radicle growth inhibition showed that, among six vegetables tested, Chinese mustard and edible amaranth were the most sensitive to glufosinate. Field mustard and cruciferous Ching-Geeng were found to be more sensitive to this herbicide than the other four vegetables when three-leaf seedlings were tested in another bioassay. In three-leaf seedlings of Ching-Geeng, accumulation of ammonium, a biochemical marker for glufosinate toxicity because of its inhibition of glutamine synthetase, showed a linear regression to the log-transformed concentrations of glufosinate ranging from 7.5 × 10−5 to 1.5 × 10−3 M. For the detection of glufosinate lower than 7.5 × 10−6 M, a linear regression was observed between ammonium accumulation and the applied concentration, instead of the log-transformed value, of gl...

Malbrancheamide, a new calmodulin inhibitor from the fungus Malbranchea aurantiaca

Bioassay-directed fractionation of an ethyl acetate extract (mycelia and broth) of the fungus Malbranchea aurantiaca led to the isolation of the novel phytotoxic alkaloid (5a S,12a S,13a S)-8,9-dichloro-12,12-dimethyl-2,3,11,12,12a,13-hexahydro-1 H,6 H-5a,13a (epiminomethano)indolizino[7,6b]carbazol-14-one ( 1 ) of the brevianamide series. The phytotoxin was given the trivial name of malbrancheamide ( 1 ). The structure of 1 was unequivocally established by UV, NMR, MS and X-ray studies. The absolute configuration was established by X-ray analysis according to the method of Flack. According to the conformational studies using molecular mechanics analyses, 1 exists in one preferred conformation, which was optimized by DFT calculations. Compound 1 caused moderate inhibition of radicle growth of Amaranthus hypochondriacus (IC 50=0.37 μM) and inhibited the activation of the calmodulin-dependent enzyme PDE1 (IC 50=3.65±0.74 μM). This effect was comparable to that of chlorpromazine (IC 50=2.75±0.87 μM) a well characterized CaM antagonist. The inhibition mechanism of 1 was competitive with respect to CaM according to a kinetic analysis.

Barley Autotoxicity as Influenced by Varietal and Seasonal Variation

AbstractBarley (Hordeum vulgare L.) is widely cultivated in the semi‐arid region of Tunisia for grain production and grazing, which often occurs during the same season. We previously demonstrated autotoxic effects of barley among varieties. The present study was conducted to test the effects of barley variety and seasonal variation on the expression of autotoxicity by barley. Four barley varieties were grown in a field experiment over three growing seasons (1999–2000, 2000–01, 2001–02). In the laboratory, germination and seedling growth bioassays were used to assess autotoxicity potential of field‐harvested barley. Barley autotoxicity was fully expressed based on inhibition of radicle growth detected in seedling bioassays. Stems were often the most allelopathic plant component. Allelopathic activity of the barley varieties differed across growing seasons suggesting the influence of a seasonal effect due to the extent of water deficit during the dry season and monthly rainfall variability. The results suggest that when planning to integrate barley within cropping sequences, barley producers should carefully select appropriate barley varieties to minimize autotoxicity, which can be more severe under drought conditions.

Phytotoxic Activity of Bibenzyl Derivatives from the Orchid Epidendrum rigidum

A whole plant chloroform-methanol extract of the orchid Epidendrum rigidum inhibited radicle growth of Amaranthus hypochondriacus seedlings (IC50 = 300 microg/mL). Bioassay-guided fractionation furnished four phytotoxins, namely, gigantol (1), batatasin III (2), 2,3-dimethoxy-9,10-dihydrophenathrene-4,7-diol (9), and 3,4,9-trimethoxyphenanthrene-2,5-diol (11), along with the known flavonoids apigenin, vitexin, and isovetin and the triterterpenoids 24,24-dimethyl-9,19-cyclolanostane-25-en-3beta-ol (14) and 24-methyl-9,19-cyclolanostane-25-en-3beta-ol (15). Stilbenoids 1, 2, 9, and 11 inhibited radicle growth of A. hypochondriacus with IC50 values of 0.65, 0.1, 0.12, and 5.9 microM, respectively. Foliar application of gigantol (1) at 1 microM to 4 week old seedlings of A. hypochondriacus reduced shoot elongation by 69% and fresh weight accumulation by 54%. Bibenzyls 1 and 2, as well as synthetic analogues 4'-hydroxy-3,3',5-trimethoxybibenzyl (3), 3,3',4',5-tetramethoxybibenzyl (4), 3,4'-dihydroxy-5-methoxybibenzyl (5), 3'-O-methylbatatasin III (6), 3,3',5-trihydroxybibenzyl (7), and 3,4',5-trihydroxybibenzyl (8), were tested for phytotoxicity in axenic cultures of the small aquatic plant Lemna pausicostata. All bibenzyls derivatives except 7 and 8 inhibited growth and increased cellular leakage with IC50 values of 89.9-180 and 89.9-166 microM, respectively. The natural and synthetic bibenzyls showed marginal cytotoxicity on animal cells. The results suggest that orchid bibenzyls may be good lead compounds for the development of novel herbicidal agents.

Evaluation of Allelopathic Potential of Wood Chips for Weed Suppression in Horticultural Production Systems

Shredded and chipped wood mulches are used for weed suppression in perennial fruit crops, in urban landscapes, and occasionally in vegetable crops. Wood chip mulches with weed-suppressing allelochemicals may be more effective for weed control, especially under sustainable and organic production systems, than mulches without such properties. The objective of this study was to test for the presence of water-soluble allelochemicals in wood chips derived from tree species, often found in wood resource recovery operations in the southeastern US. Presence of allelochemicals in water eluates of woodchips and leaves was evaluated in a lettuce bioassay. Eluates of wood chips from red maple (Acer rubrum L.), swamp chestnut oak (Quercus michauxii Nutt.), red cedar (Juniperus silicicola L.H. Bailey), neem (Azadirachta indica A. Juss.), and magnolia (Magnolia grandiflora L.) highly inhibited germinating lettuce seeds, as assessed by inhibition of hypocotyl and radicle growth. The effects of wood chip eluates from these five species were more than that found for eluates from wood chips of black walnut (Juglans nigra L.,) a species previously identified to have weed-suppressing allelochemicals. Tests on red cedar, red maple, and neem showed that water-soluble allelochemicals were present not only in the wood but also in the leaves. In greenhouse trials, red cedar wood chip mulch significantly inhibited the growth of florida beggarweed (Desmodium tortuosum DC.), compared to the gravel-mulched and no-mulch controls.

Phytotoxins from Hofmeisteria schaffneri: Isolation and Synthesis of 2‘-(2‘ ‘-Hydroxy-4‘ ‘-methylphenyl)-2‘-oxoethyl Acetate

Activity-directed fractionation of a CH(2)Cl(2)-MeOH (1:1) extract of Hofmeisteria schaffneri led to the isolation of a new phytotoxin characterized as 2'-(2' '-hydroxy-4' '-methylphenyl)-2'-oxoethyl acetate and designated the trivial name of hofmeisterin (1). In addition, the known compounds beta-carotene, euparin, and 3',4',4a',9a'-tetrahydro-6,7'-dimethylspiro[benzofuran-3(2H),2'-pyrano[2,3-b]benzofuran]-2,4a'-diol (2) were obtained. The identification of the isolates was accomplished by spectroscopic methods. The structure of 1 was unequivocally confirmed by synthesis. The methyl derivative 1a was also synthesized following the same strategy. Compounds 1 and 2 inhibited radicle growth of Amaranthus hypochondriacus (IC(50) = 3.2 x 10(-4) and 1.2 x 10(-5) M, respectively) and significantly inhibited activation of the calmodulin (CaM)-dependent enzyme cAMP phosphodiesterase (PDE) with IC(50) values of 4.4 and 4.22 microM, respectively.

Phytotoxins from the fungus Malbranchea aurantiaca

Bioassay-directed fractionation of an ethyl acetate extract from cultures of the fungus Malbranchea aurantiaca led to the isolation of two phytotoxic compounds, namely, 1-hydroxy-2-oxoeremophil-1(10),7(11),8(9)-trien-12(8)-olide ( 1) and penicillic acid ( 2). The structure of 1 was established by spectroscopic and X-ray crystallographic analyses. Metabolites 1 and 2 caused significant inhibition of radicle growth of Amaranthus hypochondriacus with IC 50 values 6.57 and 3.86 μM, respectively. In addition, 1 inhibited activation of the calmodulin-dependent enzyme cAMP phosphodiesterase (IC 50 = 10.2 μM).